There are a lot of factors that effect this especially lately. DKIM is just one of a few records that need managing. SPF and DMARC can also play a part.
Also, lately, if your emails even mention the c19 virus or anything on that subject, your emails will be sent to junk by most providers but most certainly by google/gmail, so content is a big factor here (not just c19 but other topics can have similar results).
Finally, your domain reputation is also a big part of the equation. You can check your domains reputation by going to googles postmaster tools Click here to do that